tests: support Linux kernels with CONFIG_IPV6=n

Detecting the presence of constants in C headers is insufficient,
as a Linux kernel can be built with CONFIG_IPV6=n

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65055 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/ruby/library/socket/basicsocket/setsockopt_spec.rb

@@ -237,6 +237,7 @@ describe 'BasicSocket#setsockopt' do
         @socket.getsockopt(:IP, :TTL).int.should == 255
       end
 
+      guard -> { SocketSpecs.ipv6_available? } do
         it 'sets an IPv6 boolean option' do
           socket = Socket.new(:INET6, :STREAM)
           begin
@@ -246,6 +247,7 @@ describe 'BasicSocket#setsockopt' do
             socket.close
           end
         end
+      end
 
       platform_is_not :windows do
         it 'raises Errno::EINVAL when setting an invalid option value' do

spec/ruby/library/socket/fixtures/classes.rb

@@ -50,7 +50,7 @@ module SocketSpecs
   def self.ipv6_available?
     @ipv6_available ||= begin
       server = TCPServer.new('::1', 0)
-    rescue Errno::EADDRNOTAVAIL, SocketError
+    rescue Errno::EAFNOSUPPORT, Errno::EADDRNOTAVAIL, SocketError
       :no
     else
       server.close

spec/ruby/library/socket/socket/ipv6only_bang_spec.rb

@@ -1,6 +1,7 @@
 require_relative '../spec_helper'
 
-describe 'Socket#ipv6only!' do
+guard -> { SocketSpecs.ipv6_available? } do
+  describe 'Socket#ipv6only!' do
     before do
       @socket = Socket.new(:INET6, :DGRAM)
     end
@@ -14,4 +15,5 @@ describe 'Socket#ipv6only!' do
 
       @socket.getsockopt(:IPV6, :V6ONLY).bool.should == true
     end
+  end
 end

test/socket/test_udp.rb

@@ -20,9 +20,13 @@ class TestSocket_UDPSocket < Test::Unit::TestCase
       assert_match(/AF_INET\b/, sock.inspect)
     }
     if Socket.const_defined?(:AF_INET6)
+      begin
         UDPSocket.open(Socket::AF_INET6) {|sock|
           assert_match(/AF_INET6\b/, sock.inspect)
         }
+      rescue Errno::EAFNOSUPPORT
+        skip 'AF_INET6 not supported by kernel'
+      end
     end
   end